I have a 96 GMC 5.7L 350 and I am going to be buying a new set of heads soon for my 383. I don't know what casting # is on my type of heads. I've been on ebay snooping around and saw that most of them are casted with 906 on them. Is this the correct casting # for my engine? Also is there anyone here selling a pair of these heads bare? Thanks

 

I dunno bout the cast #'s but i am prety sure the vortec heads have a different water flow path then regular small block heads,you need to get a vortech intake to match the heads. I am not sure but i think that that the vortech moter has a reverse water pump. if you want a decent et of heads look for some zz3 heads they work good.

 

no the lt1 is reverse water not the truck motors

 

From what I remember the "906" castings should be avoided because they kill low end TQ and flow. You want a set of "062" casted heads. In 2000 I built a 383 for my Monte SS with vortec heades and it made 360hp to the tire with a huge cam and home porting. Also your heads need to be adressed depending on what size cam you use. I believe stock vortec heads are only good to like .415 valve lift. If you want to go higher you must trim the valve guides down a 1/4" and this will allow up to .550" of lift.

hope this helps

 

correct....

 

not to be a di$k but use the search botton cause someone just was talking about this a while back and u did not have to shaved the guides down and was able to use 918 springs.
the search botton is a friend a good friend

 

If you install the Compcams 915 or 918 beehive s[ringssprings on teh 96-2000 Vortec 350 heads along with their respective locks and retainers, 0.550" of lift is attainable on teh Vortec heads, with no machining whatsoever
these valves are designed for GEN 3 engines but are a drop in replacement for the vortec L31 iron heads.

One of teh numbers has press in exhaust seats which can reduce low lift flow, a rotary porting tools will take care of that.

Look into the GM HT 383, it has 4 bolt mains, PW(powdered metal rods, stronger than the HIPO pink rods before them) and hyper pistons. Its is rated at 340 hp@4500 and 435 lb/ft @4000 rpm and will drop rightinto your 1996. If you are using the stock intake manifold, make sure you stay under the 330 rwhp or 400 crank hp limit, the poppet injectors and the upgraded multec injectors are rated at 19 lb/hr and wont provide enough fuel for more than that.
A Ramjet or Marine Intake is needed to go over that HP. Pocket ported Vortec heads with the GM otcam and headers and exaust with a tune will put you at 320-330 rwhp and make an extended can truck run 14 flats at 97 mph with a tune.

post back with any questions
peace
Hog

 

When I did my heads I had to machine down the valve guides. The cam I used had a about a .525 lift from what I remember and physically made the rocker arm bottom out on the valve guide. I never heard of using the 918 behive springs but I did this engine back in 2000 so I guess things are done differently now.

Here is a good article I looked up really quick...

http://chevyhiperformance.com/howto/97458/

 

ok guys I take back the coment, Sorry for the wrong info......

 

Thanks for all the great info guys. So the 062 casting #'s are better to go with? I am going with the marine intake and as far as the cam is concerned I haven't decided yet.